The invention relates to a dishwashing machine having at least one pumping device for pumping dishwashing solution, the pumping device having at least one pump having a brushless permanent magnet motor. The invention also relates to an electronic controller and a pump.
Pumps of pumping devices of dishwashing machines are usually implemented as shaded-pole motors or synchronous motors. Shaded-pole motors have the advantage of a high pumping rate and a defined running direction. This makes it possible to arrange the outlet tangentially on a pump housing. The problem with using shaded-pole motors is the fact that they are mostly “dry-running” devices, which means that costly sealing measures are needed. If the seal cannot be maintained, then the pump may fail.
Synchronous motors, on the other hand, are mostly “wet-running” devices, which allows a simpler mechanical design for a pump, because such costly sealing measures are not needed. Because of its operating principle, it is inherently impossible to define the running direction of an impeller of the pump. This has the advantage that if there is a blockage, e.g. when pumping out food residues, there is a chance that the blockage may be cleared by a change in the direction of rotation of the impeller. On the other hand, the randomly adopted running direction of the impeller means that the outlet must be arranged centrally on the pump housing. As a result of the adverse flow dynamics of this arrangement, synchronous motors can provide a low pumping rate compared with shaded-pole motors.
Also known from the prior art are brushless permanent magnet motors (brushless direct current motors, brushless alternating current motors, permanent magnet synchronous motors), which have been proposed for use in washing machines and dishwashing machines. The rotor of a brushless permanent magnet motor comprises one or more permanent magnets; the stator comprises a plurality of electromagnets. The electromagnets in the stator are commutated via an electronic controller e.g. using block commutation or sinusoidal commutation. Brushless permanent magnet motors therefore have the advantage that the direction of rotation of the stator, to which the impeller of the pump is fixed so as to rotate with it, can be set by the electronic controller. Furthermore, the pumping rate of a pump having a brushless permanent magnet motor can be controlled by adjusting the speed of the stator.
The principle of using brushless permanent magnet motors in domestic appliances is known from the prior art.
DE 195 33 076 A1 discloses a circuit for driving a brushless synchronous motor for a pump in a washing machine.
DE 198 46 831 A1 discloses a method for determining the rotor position of synchronous motors.
JP 2004278539A proposes the use of a pump having a brushless motor in a dishwashing machine. The dishwashing machine shown in this case makes use of a single pump for circulating the dishwashing solution in a closed water circuit and for pumping out the dishwashing solution from the dishwashing machine.
EP 1 502 535 A2 describes a circulating pump having a brushless motor, which can be used to control the fluid flow in a dishwashing machine. In particular, it is possible to deliver dishwashing solution optionally to the upper rack, the lower rack or both dishwasher ranks.
In addition, JP 2001276479 A discloses a pump having a brushless motor that has an axially arranged inlet and an outlet arranged tangentially on the pump housing.